CN203422336U - Laser scanning thermal wave imaging system based on dynamic sub-window technology - Google Patents
Laser scanning thermal wave imaging system based on dynamic sub-window technology Download PDFInfo
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- CN203422336U CN203422336U CN201320519593.3U CN201320519593U CN203422336U CN 203422336 U CN203422336 U CN 203422336U CN 201320519593 U CN201320519593 U CN 201320519593U CN 203422336 U CN203422336 U CN 203422336U
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Abstract
The utility model relates to a laser scanning thermal wave imaging system based on dynamic sub-window technology. The laser scanning thermal wave imaging system comprises a laser used for exciting thermal waves on the surface of an object to be measured; a light beam reshaping device used for adjusting the shape of a necessary laser focal spot formed by the laser beam on the surface of the object to be measured; a light beam deflecting device used for deflecting the laser spot to scan the surface of the object to be measured; a scanning control unit used for controlling the light beam deflecting device; a data processing unit used for controlling the system and analyzing and processing a collected thermal wave image; and a thermal imager used for collecting the thermal wave image of the object to be measured. The laser scanning thermal wave imaging system is characterized in that the size and position of a collection sub-window of the thermal imager are tracked and adjusted dynamically according to the position and moving speed of a laser focal spot image on an infrared array detector.
Description
Technical field
The present invention relates to a kind ofly based on dynamic window thermal imaging, the thermal wave imaging system that adopts scanning laser beam to carry out thermal excitation, for testee is carried out to Non-Destructive Testing, belongs to the technical field of Infrared Non-destructive Testing.
Background technology
The ultimate principle of heat wave tomography Dynamic Non-Destruction Measurement is, first adopts thermal excitation source to carry out PULSE HEATING to testee surface, forms the temperature difference of surface and testee inside, and heat energy is flowed from surface to interior of articles.If the thermal characteristic of interior of articles has heterogeneity, such as defects such as fracture or spaces, the propagation of hot-fluid will be affected, and part hot-fluid can be reflected back to the surface of object.Utilize thermal imaging system continuous acquisition from the heat radiation images on testee surface, then by analyzing the temperature variant characteristic of these images, can obtain heat wave by the time and intensity of interior of articles defect reflection, thereby judge size and the characteristic of these defects.
Fast development along with industry such as new material, new forms of energy, high-speed railway, nuclear industry and Aero-Space, increases day by day to the requirement of Dynamic Non-Destruction Measurement.The advantages such as thermal wave detection technology has that detection speed is fast, imaging area is large, noncontact and long-range detection, are widely used.Compare traditional nondestructiving detecting means, such as ultrasound wave, eddy current, the technology such as X ray, infrared thermal wave imaging technique has unique advantage.And this technology is especially very effective to the detection of compound substance.The utilization of compound substance has become modern aerospace field and has equipped one of advanced important symbol.Along with various particulate metal materials and compound substance are in the application at the positions such as fuselage, wing, turbo blade, storepipe, aeromotor jet pipe, turbo blade and airframe structure, the requirement of Non-Destructive Testing is progressively increased.At the compound substance of new energy field, apply also at Fast Growth, as the blade of aerogenerator is mainly all made by glass fiber resin packing material at present equally.Conventionally compound substance is mode or the honeycomb sandwich construction that adopts multi-layer fiber gummed, has high strength and lightweight advantage.Owing to often can producing inherent vice in the process manufacturing and using, as layering, unsticking, crack etc., greatly affected intensity and the serviceable life of material.Although to the Non-Destructive Testing of compound substance, can adopt traditional Ultrasonic Flaw Defect, this technical requirement probe contact testee, point by point scanning, wastes time and energy.For baroque compound substance, as cellular sheet material, ultrasonic technology cannot detect effectively.
When heat wave tomography, characteristic per sample has two kinds of thermal excitation modes.For the material of thinner sample, particularly high thermal conductivity, such as semiconductor wafer and solar silicon wafers etc., adopts very short pulse mode of thermal excitation time, otherwise the echo of heat wave while arriving surface thermal excitation also do not finish, impact detects.And for sample thicker or heat conduction rate variance, the variation of heat wave is slow, high to the energy requirement of thermal excitation, so conventionally adopt continuous thermal excitation source, as Infrared High-Power lamp etc., long-time heating continuously, and then carry out image acquisition, sampling rate can be very slow.
Detection to quick variation heat wave signal need to solve two problems, the thermal excitation of high-energy short pulse and high-speed image sampling.For the thermal excitation of high-energy short pulse, the product on foreign market all adopts high-energy flashlamp as pulse heat driving source at present.For example, but this high-energy flashlamp has a lot of limitations, and its gross energy is limited, the area of each test can not be too large; Beam divergence is inhomogeneous, can not telekinesy; The flash pulse cycle is extremely short and non-adjustable, and too high peak power can cause the damage of sample; The serviceable life of fluorescent tube is limited, and equipment volume is huge, it is mobile etc. to be difficult for.And for the problem of high-speed image sampling, only have at present and adopt the thermal imaging system with high frame frequency function.This thermal imaging system is very expensive, and the image resolution ratio of output is along with the raising of frame frequency significantly declines.
High power semiconductor lasers has obtained rapid development in recent years, makes this type of laser instrument when power increases substantially, price fast-descending.Laser instrument is compared with traditional thermal excitation light source has that wavelength can be selected, intensity can be modulated, and light beam can be assembled and the advantage such as can scan.
Existing a small amount of thermal wave imagine technique adopts laser scanning thermal excitation at present, as United States Patent (USP) 3,808,439,6,343,874,6,419,387 etc., all introduced and adopted the method for laser scanning thermal excitation to carry out thermal wave imaging, one of them typical system as shown in Figure 4, has wherein adopted polynary photodetector.But the laser beam of this invention and infrared image all pass through scanning system, the receiving aperture of infrared eye is subject to the considerable restraint of tilting mirror, and in these methods, all could not solve the key issue of heat wave tomography, the detection that is particularly directed to shallow cosmetic bug must adopt the problem of high frame frequency thermal imaging system.
Summary of the invention
Object of the present invention is exactly the deficiency for above-mentioned existing heat wave Dynamic Non-Destruction Measurement, and a kind of thermal wave imaging lossless detection method that simultaneously meets pulse heat excitation and high speed infrared image acquisition is provided.The method adopts high power laser as thermal excitation source, by controlling beam deflection device, rapid scanning is carried out in the surface of sample, realizes pulse heat excitation.The position that thermal imaging system gathers subwindow is dynamically set again, makes it follow the tracks of the scanning of laser facula, then by the heat wave image to gathered, carry out correction and Image Mosaics and the reconstruction of time delay, reach the object of high frame frequency image acquisition.
The temporal resolution of traditional thermal wave imagine technique is decided by the frame frequency of thermal imaging system, and the frame frequency of conventional thermal imaging system is limited, as in 25-60Hz left and right, is not suitable for the thermal wave imaging Non-Destructive Testing of thinner or sample that thermal conductivity is larger.And high frame frequency thermal imaging system is except very expensive, the image resolution ratio of its output is along with the raising meeting of frame frequency significantly declines.The technology of the present invention has effectively solved this problem, makes in the situation that using conventional thermal imaging system, and the temporal resolution of thermal wave detection is greatly improved.
The speed of laser scanning can characteristic per sample be selected, if sample heat conduction is fast and have the defect compared with shallow-layer, can adopt light pencil rapid scanning.If sample temperature conductivity is low, defective locations is deep, can adopt angle pencil of ray slow scanning, to there is more thermal excitation energy.Except taking linear beam one-dimensional scanning, also can adopt point-like focal beam spot to carry out two-dimensional scan.
Accompanying drawing explanation
Fig. 1 (a), (b) is heat wave signal temporal evolution schematic diagram.
Fig. 2 is for adopting the prior art systems schematic diagram of flashlamp excitation thermal wave imaging.
Fig. 3 is for adopting the prior art schematic diagram of flashlamp excitation thermal wave imaging.
Fig. 4 is for adopting the thermal wave imaging prior art systems schematic diagram of scan laser thermal excitation.
Fig. 5 is systematic schematic diagram of the present invention.
Fig. 6 (a), (b) is light path principle figure of the present invention.
Fig. 7 (a), (b) is the method schematic diagram of a kind of definite laser scanning speed of the present invention and position.
Fig. 8 (a), (b) is all scan mode schematic diagram of the present invention two.
Fig. 9 is the systematic schematic diagram of an embodiment of the present invention.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described.
Shown in Fig. 1 (a) is the time dependent relation of heat wave signal.After of short duration pulse heat excitation, sample surfaces temperature raises rapidly, then starts to decline.If sample interior does not have defect, heat wave signal intensity is as shown in curve 31.If but sample interior exists thermal resistance defect, as space or crackle etc., will hinder heat wave to propagate to sample interior, the variation of sample surfaces heat wave signal is as shown in curve 32.The result that curve 31 and 32 subtracts each other is as shown in the curve 33 in Fig. 1 (b).According to the peak value S of curve 33
osize and the time t that occurs of peak value
ocan learn the information of relevant defect, as the degree of depth and size etc.Therefore in order to realize heat wave tomography, temperature decline curve 31 and 32 must can be measured.
In prior art, the system architecture of the heat wave tomography of employing flashlamp thermal excitation and ultimate principle are respectively as shown in Figures 2 and 3, after 104 heating of 102 pairs of samples of high-energy flashlamp, the heat energy absorbing along with sample surfaces starts to propagate to sample interior, surface temperature starts to decline, as shown in curve 36.Continuous acquisition a series of images 34 in the process that thermal imaging system 106 declines in temperature, then the heat wave signal 35 use formula fittings corresponding to same pixel in this series of images 34 are got up, the temperature variant curve 36 of this pixel heat wave signal can be obtained.Can find out, what conventional heat wave chromatography imaging technique adopted is once to excite, the method for image acquisition repeatedly, and the minimum interval of image acquisition is a frame frequency cycle.Therefore the frame frequency cycle of thermal imaging system must be much smaller than the period of change of heat wave signal, otherwise can cannot accurately obtain curve 36 very little because of sampled point.Therefore to some heat wave signal intensities than sample faster, must adopt the thermal imaging system of high frame frequency, but when the frame frequency raising of thermal imaging system, conventionally adopt subwindow mode, i.e. the pixel of imaging can greatly reduce, and causes the area of imaging and the decline of resolution.
The peak power of common high power laser is limited, particularly on average to sample surfaces.In order to form pulse heat excitation, first focus of the light beam on a line, the power density of unit area can improve hundreds of times like this.Can certainly further focus on a point, power density raising is more like this, but need to adopt two-dimentional scanister.When laser wire harness is during at sample surfaces rapid scanning, on sample, the suffered thermal excitation of any point is of short duration, therefore can regard pulsed as.
Shown in Fig. 5 is a kind of embodiment schematic diagram of system of the present invention, comprises superpower laser 21, light-beam forming unit 26, beam deflection device 25, thermal imaging system 22, data processing unit 20 and scan control unit 24 etc.Laser beam 27 forms fan-shaped in-line laser focal spot 30 by light-beam forming unit 26, beam deflection device 25 is controlled in scan control unit 24, and then control the laser scanning district 29 of laser focal spot 30 on testee 28 and line by line scan, the heat wave signal exciting is received and is delivered to that data processing unit 20 carries out data processing and heat wave is analyzed by thermal imaging system 22.
In order to improve the image acquisition frame frequency of thermal imaging system 22, the method that the present invention adopts dynamic acquisition subwindow 41 to follow the tracks of laser focal spot 30 track while scans, be that every two field picture only gathers a part on infrared array detector 40, gather the region shown in subwindow 41, this gathers subwindow 41 and follows the scanning of laser focal spot 30 and move.
Figure 6 shows that the light path schematic diagram of apparatus of the present invention imaging moiety.The image 42 of laser focal spot 30 projects on infrared array detector 40 through the lens 43 of thermal imaging system 22, gather subwindow 41 and be selected in laser focal spot image 42 around, Fig. 6 (a) and (b) represent respectively two different moment, gathers subwindow 41 and the relative position of laser focal spot image 42 on infrared array detector 40.When laser focal spot 30 scanning, corresponding laser focal spot image 42 also moves on infrared array detector 40, therefore gathers subwindow 41 and is also dynamically following laser focal spot image 42 and move.Can be much smaller than the line number of infrared array detector 40 owing to gathering subwindow 41, the frame frequency of therefore sampling is improved greatly.The thermal imaging system of 640 X 480 of 50 hertz of frame frequencies for example, when gathering subwindow 41 and be made as 640 X 20, frame frequency can improve 24 times, 1200 hertz.Because sample window 41 is followed laser focal spot 30 and moved together in the laser scanning district 29 of whole testee 28, therefore image is after treatment the whole laser scanning of complete covering district 29, and the resolution of final heat wave image is constant.Unlike the prior art that adopts flashlamp thermal excitation, in order to improve frame frequency, using the imaging of subwindow mode simultaneously, factor the window's position is fixed, and the region of imaging significantly reduces, and resolution declines to a great extent.
The size that gathers subwindow 41 is decided by material thermal characteristic and laser scanning speed, when material thermal diffusivity is large or when very thin, for example metal material or various film and coating, the sweep velocity of laser focal spot 30 needs to improve, gathering subwindow 41 can reduce simultaneously, to increase the sample frequency of image.
In the heat wave image gathering at above-described embodiment, because laser focal spot is moving, the heat wave signal of each pixel or pixel column and the time delay between thermal excitation are different, for to revising these time delays, need to know position and the sweep velocity of laser focal spot 30 in heat wave image.This can pass through accomplished in many ways.First, in the situation that known testee 28 is to the distance of beam deflection device 25, can adopt deflection angle and the rotational angular velocity of the prior beam deflection device 25 of calibrating, in conjunction with the scanning sequence relation between beam deflection device 25 and thermal imaging system 22, by calculating, obtain.
Reasonable way is the heat wave image from collecting, and according to the position of laser focal spot 30, determines, the position of laser focal spot 30 is also the strongest place of heat wave signal conventionally.As shown in Figure 7 (a), when laser focal spot 30 scans from top to bottom, if read heat wave signal along direction of scanning, obtain curve as shown in Figure 7 (b) shows, wherein the signal maximum value 50 at laser focal spot 30 places, place is for the strongest.Therefore can carry out matching to taking out data along the direction of scanning of laser facula 30 in heat wave image, find out heat wave signal maximum value 50 residing positions.By contrasting the change in location of signal maximum value 50 in the image of two frame known interval, can learn the translational speed of laser focal spot 30.
Another one method is the track while scan adopting the video camera 52 synchronous recording laser faculas 30 of thermal excitation wavelength sensitive, and calculates thus position and the sweep velocity of laser facula 30, as shown in Figure 9.The scanning area of video camera 52 and thermal imaging system 22 is through accurately check and correction, and both frame frequencies are preferably synchronous.The image of video camera 52 can also be used to the surface optics characteristic of the homogeneity of laser facula 30 and testee 28 to record for proofreading and correct.
The laser focal spot 30 that above-mentioned thermal wave imaging system embodiment adopts is the basic straight lines that are wider than laser scanning district 29 that wait, and beam deflection device 25 carries out one-dimensional scanning.As required, such as in the high thermal excitation intensity of needs or when compared with large sample, laser focal spot 30 can be narrower than laser scanning district 29, and now beam deflection device 25 carries out two-dimensional scan, as shown in Figure 8 (a).Laser focal spot 30 can also scan by compartment simultaneously, after finishing, sweeps first row the 3rd row, the 5th row etc., and then later sweep secondary series, the 4th row etc., until cover a whole two field picture, scan method can make the adjacent scan registration of two-phase region have longer cooling release time like this, in order to avoid this region heat wave distorted signals.
Laser focal spot 30 can be also a shaped laser spot, adopts the method for two-dimensional scan, as shown in Figure 8 (b) shows.Gather the peripheral region that subwindow 41 may be selected in laser focal spot 30, by detection laser focal spot 30 sides and heat wave signal intensity above, can obtain more information.In a word, laser focal spot 30 can be various shapes, and scanning can be also any direction.
In order to narrate conveniently, above embodiment adopts laser as thermal excitation source.In fact any energy beam that can form focal spot and can be absorbed by object can be as thermal excitation source, as electron beam, ion beam, beam of sound etc.
Claims (4)
1. a laser scanning thermal wave imaging system, comprising:
Laser instrument (21), described laser instrument (21) is for encouraging heat wave on testee (28) surface;
Light-beam forming unit (26), described light-beam forming unit (26) forms the shape of required laser focal spot (30) for adjusting laser beam (27) on testee (28) surface;
Beam deflection device (25), described beam deflection device (25) scans testee (28) surface for deflection laser focal spot (30);
Scan control unit (24), described scan control unit (24) is for controlling described beam deflection device (25);
Data processing unit (20), described data processing unit (20) is for controlling system and the heat wave image gathering being carried out to analyzing and processing;
Thermal imaging system (22), be used for gathering the heat wave image of described testee (28), it is characterized by, the size of the collection subwindow (41) of described thermal imaging system (22) and position are dynamically followed the tracks of and are adjusted according to position and the translational speed of the upper laser focal spot image (42) of infrared array detector (40).
2. laser scanning thermal wave imaging system according to claim 1, it is characterized by, described light-beam forming unit (26) makes laser beam (27) form the linear laser focal spot (30) substantially wide with laser scanning district (29) on testee (28) surface, and described beam deflection device (25) is carried out one-dimensional scanning.
3. laser scanning thermal wave imaging system according to claim 1, it is characterized by, described light-beam forming unit (26) makes laser beam (27) form on testee (28) surface the laser focal spot (30) that dimension is less than laser scanning region (29), and described beam deflection device (25) is carried out two-dimensional scan.
4. laser scanning thermal wave imaging system according to claim 1, is characterized by, and further comprises the video camera (52) to laser instrument (21) output wavelength sensitivity.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104422715A (en) * | 2013-08-23 | 2015-03-18 | 南京诺威尔光电系统有限公司 | Laser scanning thermal wave imaging method and apparatus based on subwindow technology |
| CN106896138A (en) * | 2015-12-20 | 2017-06-27 | 南京诺威尔光电系统有限公司 | One kind scanning thermal excitation infrared imaging detecting system and method |
| CN113916937A (en) * | 2021-08-24 | 2022-01-11 | 中国人民解放军陆军装甲兵学院 | Crack detection method, crack detection device, electronic equipment and storage medium |
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2013
- 2013-08-23 CN CN201320519593.3U patent/CN203422336U/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104422715A (en) * | 2013-08-23 | 2015-03-18 | 南京诺威尔光电系统有限公司 | Laser scanning thermal wave imaging method and apparatus based on subwindow technology |
| CN106896138A (en) * | 2015-12-20 | 2017-06-27 | 南京诺威尔光电系统有限公司 | One kind scanning thermal excitation infrared imaging detecting system and method |
| CN113916937A (en) * | 2021-08-24 | 2022-01-11 | 中国人民解放军陆军装甲兵学院 | Crack detection method, crack detection device, electronic equipment and storage medium |
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Address after: 210046, A, building 10, 6-3, Xing Zhi Technology Park, Xing Zhi Road, Nanjing economic and Technological Development Zone, Jiangsu, China Patentee after: Nanjing Newell Optical System Co.,Ltd. Address before: 501 room 8, No. 210038, Heng Fei Road, Nanjing economic and Technological Development Zone, Nanjing, Jiangsu Patentee before: Nanjing Newell Optical System Co.,Ltd. |
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Granted publication date: 20140205 |
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